>R. Measures wrote:
>>** The grid does not and can not draw current when a competent
>>operator sets the grid potential just above the level where it can draw
>>grid-current with the max PEP drive that's available.
>
>That is only true if the grid input circuit is guaranteed to be able to
>soak up all possible levels of drive without allowing grid current...
** So you are essentially saying that if the grid terminating resistor
is blown away by the exciter, the grid driving potential could rise to a
higher level and grid-current could flow? Although this seems possible
with exciters that do not have an SWR-foldback, I have not seen such,
Ian. Have you? Would not such a scenario require that the
grid-terminator be grossly undersized?
>but that also has disadvantages: either the exciter runs flat-out and
>generates unnecessary IMD of its own, or else the exciter runs at a
>lower level and the amplifier is seriously under-driven.
** Why would the exciter run flat-out if a competent person set the
power limit control in or on the exciter to the level prescribed?
>
>I truly cannot see why anyone should design (or defend) a high-impedance
>bias supply whose voltage regulation will collapse at the first trace of
>either normal or negative grid current.?
** Because when the manufacturer of the tube specifies a maximum AB1
bias supply impedance, there is quite probably a sound engineering reason
behind it. // Ian: Hello! There is No "normal" grid current in a
Class AB1 amplifier.
> What's the point, when a
>better-regulated supply is just as easy
>
** Regulated is never as easy as unregulated. As I see it, using a
regulated supply where one is not indicated is hardly good engineering
practice. Why guild a lilly?
- In a Class AB1 linear amplifier, the potentials that need to be held
closely are the screen-V and the filament-V.
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